This invention relates to rotary torque transmitting devices in general and is particularly directed to a damper arrangement for these devices.
In conventional passenger cars and trucks, objectionable driveline vibrations may occur at certain speeds and load conditions. Some of these disturbances may be eliminated or reduced to an acceptable level with the incorporation of a torsional damper in the driven disc portion of the vehicle clutch. Damping is normally provided by a plurality of circumferentially spaced coiled springs operatively connected between relatively rotatable elements of the clutch driven disc assembly.
Clutches with dampers are widely used in all types of power transmissions systems. In recent years, particularly in the heavy duty field, conventional spring dampers have not performed satisfactorily when used with the newer higher torque engines. Due to greater horsepower output, these engines operate in a critical torsional range and, as a result, impose considerably higher loads on the spring damper than previous engines. This translates into greatly increased stresses on the damper springs which can increase damper spring failure. Additional clutch damage and rapid wear of the associated transmission input shaft and vehicle drive line components may follow.
Attempts have been made to increase the torque capacity of heavy duty clutch driven disc assemblies but, for one reason or another, have not been entirely satisfactory.
Known devices have increased the torque capacity by disposing a second smaller diameter coil spring within the primary spring. Such a design is advantageous because it requires no additional space and can be used in the restricted axial space required in present passenger car and light truck applications.
Other devices are known which are designed specifically for heavy duty applications. These are, however, more complex and further require additional radial and sometimes axial space ordinarily not available in heavy duty clutch applications. Additional capacity is built into driven discs of this type by providing two or more radially spaced sets of coaxial springs with each set designed to come into play during various stages of relative rotation between the rotary clutch disc elements. Not only are these more complex but, as stated, they also pose space limitation problems since the radial diameters must be increased to accomodate the added spring sets.
While the coaxial spring concept is not new, it has been found that, due to the different spring diameters, the most satisfactory drive surface area is not always provided for both springs. In some instances, because of the spring end configuration and the constant loads being applied to the cover opening side walls by the spring ends, the localized contact points are susceptible to damage and as a result, premature clutch cover and spring failure.
It is an object of the present invention to provide a clutch driven disc with an improved coaxial damper spring mounting which will increase the drive surface area for both springs and not require any additional space to accomplish the desired result.